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2000 noma highrider
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516 Posts
Discussion Starter · #1 ·
Hey all,

within the last week or so ive noticed ive went from 16.4mpg(mixed) to a staggering 9.2mpg!

my question is what would cause so dramatic drop in fuel mileage?
-Tires are properly inflated
-new air filter
-fuel filter is newer
-been driving like a old person.....

Now, the truck is a tick over 110,000 miles and im wondering if bad cap/rotor or even spark plugs would cause this drop? Ive noticed since ive gotten the truck its had a weird idle(gets a stumble every once in a while)

thanks all:)
 

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Sometimes I'm mean...alot
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Fuel Filter, Fuel Pump or Catalytic Converter can all contribute to a suden loss of mpg.
 

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2000 noma highrider
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516 Posts
Discussion Starter · #3 ·
Fuel Filter, Fuel Pump or Catalytic Converter can all contribute to a suden loss of mpg.
welp....

--filter is almost brand new, changed when fuel pump was swapped in
--fuel pump is less than year old
--and cat converter has been gutted over a year now.....with rear o2 sensor tricked using spark plug "non foulers"
 

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do your self a favor and check your spark plugs, wires, cap and, rotor. also pull the throttle body hat off and look down inside of the intake and see if the injectors are leaking.

also do you have a k&n filter or an oil filter? if so i would try and clean the MAS as it could be dirty.
 

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2000 noma highrider
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516 Posts
Discussion Starter · #5 ·
ok time for update for those helping(thank you)

-changed plugs(original 43-932) eek....electrodes were toast but nice light brownish, replaced with acdelco 43-933

-cap/rotor replaced(old had deposit build up)

-wires replaced with bosch....cha ching :(

i might change fuel filter again....



Truck is running tick better but no better MPG:rant: I noticed the rev/parking lot cough is still here.

Ok ill explain as best i can without a video

if you rev the truck past 2100rpm, let off gas and try to catch rpm before idle the truck "loads up". It coughs, sputters and shakes like its flooding out. But if you play with the gas petal enough you can keep motor running and all of the sudden the computer finally figures out whats going on and saves motor smoothing it out.

Now for the parking lot issue.
-When driving real slow though a parking lot or such and keeping the petal steady it seems to missfire and then come back. The motor will be running smooth and out of now where feels as someone has bumped the key off and on really quickly.

i have been dumping money on this truck and its really pissing me off. I bought a "newer" truck thinking i would have less problems than my old 89 blazer. :(
 

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Sometimes I'm mean...alot
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did you ever check your fuel pressure?
 

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fuel pressure could cause this. also when it is acting up unplug the MAF sensor and see if the issue goes away now this will set the check engine light but it is worth a try and see if this could be your issue
 

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2000 noma highrider
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516 Posts
Discussion Starter · #9 ·
fuel pressure could cause this. also when it is acting up unplug the MAF sensor and see if the issue goes away now this will set the check engine light but it is worth a try and see if this could be your issue
never thought of this......

BIG UPDATE.....turns out my battery has been taking a dump and i didnt see it. Voltage has been kinda odd lately but finally crapped out tonight leaving me stranded after work for 3 hours. Could a crap battery not let ECU work correctly?
 

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never thought of this......

BIG UPDATE.....turns out my battery has been taking a dump and i didnt see it. Voltage has been kinda odd lately but finally crapped out tonight leaving me stranded after work for 3 hours. Could a crap battery not let ECU work correctly?
I believe it can and it looks like you're getting a new battery so you'll know soon enough :)
 

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Sometimes I'm mean...alot
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never thought of this......
HUH? you need to actually READ the replies then.

BIG UPDATE.....turns out my battery has been taking a dump and i didnt see it. Voltage has been kinda odd lately but finally crapped out tonight leaving me stranded after work for 3 hours. Could a crap battery not let ECU work correctly?
Yes, it can cause "freak-ish" behavior...
 

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2000 noma highrider
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516 Posts
Discussion Starter · #12 ·
well ill let ya guys knows what goes on, buying a battery and MAF cleaner.

I USED to have a K&N and had to clean the maf before. Im wondering if it messed maf again before i threw it away:(
 

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2000 noma highrider
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516 Posts
Discussion Starter · #13 ·
fuel pressure could cause this. also when it is acting up unplug the MAF sensor and see if the issue goes away now this will set the check engine light but it is worth a try and see if this could be your issue
ok odd ball, truck runs fine when i pull plug for MAF. WTF?

i tried dads MAF off his 01 xtreme 4.3 with no engine codes and runs the same without an issue. without plugged in???
 

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terrible. take a lap.
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try cleaning it real good first so you don't potentially waste all that money on a new maf sensor since they're pricey?
 

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the youngest has been
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i would suggest looking into the intake manifold and looking for fuel washing.

im going to say the following based on the given information.

leaking fuel pressure regulator
leaking or stuck injectors/poppets
O2 sensors that are giving way lean readings
 

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2000 noma highrider
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Discussion Starter · #16 ·
well one big thing is WHY is the MAF not making a difference plugged IN or NOT?????

im lost because all the other vehicles ive owned wouldnt even fire up let alone run without it plugged in yet my truck drives without it plugged in???

The gas mileage seems to be back to normal.....14-15mpg but it should be better. I set cruise at 60mph on eway and baby the hell out of my truck:rant:
 

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well one big thing is WHY is the MAF not making a difference plugged IN or NOT?????

im lost because all the other vehicles ive owned wouldnt even fire up let alone run without it plugged in yet my truck drives without it plugged in???

The gas mileage seems to be back to normal.....14-15mpg but it should be better. I set cruise at 60mph on eway and baby the hell out of my truck:rant:
on most cars and trucks if the maf is unplugged the computer the computer will go into a kinda limp mode it will keep it running and drive-able and it will more than likely be rich as hell
not a 100% sure on this explanation but i am sure some one will chime in on this question and clarify this.
 
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